Engaging Same-Day Peer Ambassadors to Increase Coronavirus Disease 2019 Vaccination Among People Experiencing Unsheltered Homelessness in Los Angeles County: A Hybrid Feasibility-Evaluation Study

BACKGROUND

This study aimed to evaluate the feasibility and acceptability of engaging unhoused peer ambassadors (PAs) in coronavirus disease 2019 (COVID-19) vaccination efforts to reach people experiencing unsheltered homelessness in Los Angeles County.

METHODS

From August to December 2021, vaccinated PAs aged ≥18 years who could provide informed consent were recruited during vaccination events for same-day participation. Events were held at encampments, service providers (eg, housing agencies, food lines, and mobile showers), and roving locations around Los Angeles. PAs were asked to join outreach alongside community health workers and shared their experience getting vaccinated, receiving a $25 gift card for each hour they participated. Postevent surveys evaluated how many PAs enrolled and how long they participated. In October 2021, we added a preliminary effectiveness evaluation of how many additional vaccinations were attributable to PAs. Staff who enrolled the PAs estimated the number of additional people vaccinated because of talking with the PA.

RESULTS

A total of 117 PAs were enrolled at 103 events, participating for an average of 2 hours. At events with the effectiveness evaluation, 197 additional people were vaccinated over 167 PA hours ($21.19 gift card cost per additional person vaccinated), accounting for >25% of all vaccines given at these events.

DISCUSSION

Recruiting same-day unhoused PAs is a feasible, acceptable, and preliminarily effective technique to increase COVID-19 vaccination in unsheltered settings. The findings can inform delivery of other health services for people experiencing homelessness.

Community Health Worker Perspectives on Engaging Unhoused Peer Ambassadors for COVID-19 Vaccine Outreach in Homeless Encampments and Shelters

BACKGROUND

COVID-19 vaccination is a priority for people experiencing homelessness. However, there are barriers to vaccine access driven in part by mistrust towards clinicians and healthcare. Community health workers (CHWs) and Peer Ambassadors (PAs) may be able to overcome mistrust in COVID-19 vaccine outreach. An unhoused PA program for COVID-19 vaccine outreach by CHWs was implemented in Los Angeles using a participatory academic-community partnership.

OBJECTIVE

The purpose of this study was to evaluate CHW perspectives on an unhoused PA COVID-19 vaccine outreach program in Los Angeles.

DESIGN

This study used a participatory community conference and qualitative focus groups to understand CHW perspectives on the PA program. The one-day conference was held in November 2021.

PARTICIPANTS

Of the 42 conference participants, 19 CHWs participated in focus groups for two-way knowledge exchange between CHWs and researchers.

APPROACH

Four focus groups were held during the conference, with 4-6 CHWs per group. Each group had a facilitator and two notetakers. Focus group notes were then analyzed using content analysis to derive categories of findings. CHWs reviewed the qualitative analysis to ensure that findings represented their experiences with the PA program.

KEY RESULTS

The five categories of findings from focus groups were as follows: (1) PAs were effective liaisons to their peers to promote COVID-19 vaccines; (2) CHWs recognized the importance of establishing genuine trust and equitable working relationships within CHW/PA teams; (3) there were tradeoffs of integrating unhoused PAs into the existing CHW workflow; (4) CHWs had initial misgivings about the research process; and (5) there were lingering questions about the ethics of "exploiting" the invaluable trust unhoused PAs have with unhoused communities.

CONCLUSIONS

CHWs were in a unique position to empower unhoused PAs to take a leadership role in reaching their peers with COVID-19 vaccines and advocate for long-term employment and housing needs.

COVID-19 Vaccine Acceptability and Financial Incentives among Unhoused People in Los Angeles County: a Three-Stage Field Survey

Unhoused people have higher COVID-19 mortality and lower vaccine uptake than housed community members. Understanding vaccine hesitancy among unhoused people is key for developing programs that address their unique needs. A three-round, rapid, field-based survey was conducted to describe attitudes toward COVID-19 vaccination. Round 1 assessed vaccine brand preference, round 2 assessed intention to accept a financial incentive for vaccination, and round 3 measured vaccine uptake and assessed reasons for vaccine readiness during implementation of a financial incentive program. A total of 5177 individuals were approached at COVID-19 vaccination events for unhoused people in Los Angeles County from May through November 2021. Analyses included 4949 individuals: 3636 (73.5%) unsheltered and 1313 (26.5%) sheltered. Per self-report, 2008 (40.6%) were already vaccinated, 1732 (35%) wanted to get vaccinated, 359 (7.3%) were not yet ready, and 850 (17.2%) did not want to get vaccinated. Brand preference was evenly split among participants (Moderna 31.0%, J&J 35.5%, either 33.5%, p = 0.74). Interest in a financial incentive differed between those who were not yet ready and those who did not want to get vaccinated (43.2% vs. 16.2%, p < 0.01). After implementing a financial incentive program, 97.4% of participants who indicated interest in vaccination were vaccinated that day; the financial incentive was the most cited reason for vaccine readiness (n = 731, 56%). This study demonstrated the utility of an iterative, field-based assessment for program implementation during the rapidly evolving pandemic. Personal engagement, a variety of brand choices, and financial incentives could be important for improving vaccine uptake among unhoused people.

Examining metastatic behavior within 3D bioprinted vasculature for the validation of a 3D computational flow model

Understanding the dynamics of circulating tumor cell (CTC) behavior within the vasculature has remained an elusive goal in cancer biology. To elucidate the contribution of hydrodynamics in determining sites of CTC vascular colonization, the physical forces affecting these cells must be evaluated in a highly controlled manner. To this end, we have bioprinted endothelialized vascular beds and perfused these constructs with metastatic mammary gland cells under physiological flow rates. By pairing these in vitro devices with an advanced computational flow model, we found that the bioprinted analog was readily capable of evaluating the accuracy and integrated complexity of a computational flow model, while also highlighting the discrete contribution of hydrodynamics in vascular colonization. This intersection of these two technologies, bioprinting and computational simulation, is a key demonstration in the establishment of an experimentation pipeline for the understanding of complex biophysical events.

Environmental Exposure of Children to Toxic Trace Elements (Hg, Cr, As) in an Urban Area of Yucatan, Mexico: Water, Blood, and Urine Levels

Merida is the largest urban center in the Mexican State of Yucatan. Here domestic sewage is deposited in poorly built septic tanks and is not adequately treated. Because of contamination from such waste, water from the top 20 m of the aquifer is unsuitable for human consumption. Given this situation and because children are highly vulnerable to environmental pollution, including exposure to toxic trace elements, this study focused on evaluating the exposure of children to arsenic (As), chromium (Cr), and mercury (Hg) in water. It also evaluated the relationship between the levels of these elements in water and their concentrations in urine and blood. Among the 33 children monitored in the study, arsenic surpassed WHO limits for blood in 37% of the cases, which could result from the ingestion of poultry contaminated with organoarsenic compounds. In the case of WHO limits for Mercury, 65% of the water samples analyzed, 28% of urine samples, and 12% of blood samples exceeded them. Mercury exposure was correlated with biological sex, some lifestyle factors, and the zone in Merida in which children live. These data suggest that the levels of some toxic metals in children may be affected by water source, socioeconomic factors, and individual behavior.

Water Consumption as Source of Arsenic, Chromium, and Mercury in Children Living in Rural Yucatan, Mexico: Blood and Urine Levels

Studies investigating the correlation between metal content in water and metal levels in children are scarce worldwide, but especially in developing nations. Therefore, this study investigates the correlation between arsenic, chromium, and mercury concentrations in drinking and cooking water and in blood and urine samples collected from healthy and supposedly non-exposed children from a rural area in Yucatan, Mexico. Mercury in water shows concentrations above the recommended World Health Organization (WHO) value for drinking and cooking water. Also, 25% of the children show mercury in urine above the WHO recommended value. Multivariate analyses show a significant role for drinking and cooking water as a vector of exposure in children. Also, the factor analysis shows chronic exposure in the case of arsenic, as well as an ongoing detoxification process through urine in the case of mercury. Further studies should be done in order to determine other potential metal exposure pathways among children.

Inherently unstable networks collapse to a critical point

Nonequilibrium systems that are driven or drive themselves towards a critical point have been studied for almost three decades. Here we present a minimalist example of such a system, motivated by experiments on collapsing active elastic networks. Our model of an unstable elastic network exhibits a collapse towards a critical point from any macroscopically connected initial configuration. Taking into account steric interactions within the network, the model qualitatively and quantitatively reproduces results of the experiments on collapsing active gels.

Anomalous discontinuity at the percolation critical point of active gels

We develop a percolation model motivated by recent experimental studies of gels with active network remodeling by molecular motors. This remodeling was found to lead to a critical state reminiscent of random percolation (RP), but with a cluster distribution inconsistent with RP. Our model not only can account for these experiments, but also exhibits an unusual type of mixed phase transition: We find that the transition is characterized by signatures of criticality, but with a discontinuity in the order parameter.

Applying the concept of metamorphosis to the crustose-to-erect thallus transition of macroalgae

Metamorphosis is broadly defined as a more or less radical morphological change between 2 multicellular life stages within an organism's life phase, often marking the transition from pre-reproductive to reproductive stages. It involves structural reorganization and major physiological changes, generally under the control of endogenous and exogenous factors and often resulting in changes in habitat use. This concept has been applied to the crustose-to-erect thallus transition of some red algae and the present study evaluates the validity of such hypotheses. Available literature suggests that the crustose-to-erect thallus transition involves significant morphological and habitat changes, separating pre-reproductive and reproductive stages. The onset of the morphological changes (for example axis differentiation) appears regulated by endogenous signals (growth factors) and growth is modified by environmental factors. The algae do not exhibit structural reorganization, however, probably due to their simple morphological structure and the lack of several cell and tissue mechanisms involving cell motility. The presence of cell walls in the algae impairs cell motility and maintains the cell in a fixed position within the plant. These are important differences restricting the extension of the definition of metamorphosis to the crust-to-erect thallus transition. The above restrictions also seem to apply to other macroalgae, fungi, and terrestrial plants.

[Hypothalamic hamartoma causing precocious puberty: A case report]

Hypothalamic hamartomas are non neoplastic lesions that may cause precocious puberty with or without complex seizures, personality disorders and mental retardation. We report a 14 years old male that had a precocious puberty at the age of 11 and a prolonged episode of altered sensorium with automatism, that was diagnosed as a complex seizure. Physical examination showed a sexual development classified as Tanner stage III-IV, a height of 168 cm and a weight of 61 kg. Neurological examination was normal. A CAT scan showed a 13 x 13 x 9 mm mass in the suprasellar cistern, between the infundibulum and the brain stem, without exerting a mass effect over adjacent structures. It was diagnosed as an hypothalamic hamartoma.

Effect of dietary oils, cholesterol and antioxidant vitamin supplementation on liver microsomal fluidity and xenobiotic-metabolizing enzymes in rats

This study was undertaken to compare the effects of four oils: corn (C), olive (O), hazelnut (H) or fish (F), and the intake of two supplements: cholesterol, 1% (Ch) or dl-alpha-tocopherol acetate, 500 mg/kg, and beta-carotene, 30 mg/kg (V), on liver microsomal fluidity, cyt P450 content and aniline hydroxylase (AH), aminopyrine-N-dimethylase (AND) and UDP-glucuronyltransferase (UDP-GT) activities. Male Sprague-Dawley rats (n = 6/group) were fed semipurified diets containing 15% oil, without or with Ch or V, for 20 days. Dietary intake and feed efficiency were lower in rats fed F. Relative liver weight was higher in animals fed F, similar in O and H, and lower in the group fed C. The intake of V increased feed intake in C+V group and decreased the relative liver weight of F+V group, which also decreased with the intake of F+Ch. Ch intake increased the relative liver weight in all groups consuming vegetable oils. Cyt P450 content was higher in rats fed F. Decreased cyt P450 content was observed in C+Ch and F+Ch groups, while it augmented in H+Ch group. Mixture V increased cyt P450 in rats fed C+V, F+V and O+V. The highest membrane fluidity was observed in rats fed F. Fluidity was also higher in group H versus O or C. The intake of Ch decreased microsomal fluidity in all groups, while V induced an increase in microsomal fluidity in group O+V. Rats fed F exhibited higher enzyme activities. AND activity increased with V only in rats fed H+V, while AH activity increased with V intake in groups F+V and O+V. In the C+V group, fluidity was not affected by V, while the cyt P450 content and UDP-GT activity increased. The O+V group exhibited lower UDP-GT activity and higher fluidity and cyt P450 content. The activity of AH decreased in groups F+Ch and C+Ch. UDP-GT activity was higher in rats fed F. It diminished after the intake of Ch in H+Ch and F+Ch. These results indicate that although AH and AND act in the same microsomal metabolic pathway, their localization into the membrane may be determinant of their activity and the response to dietary lipids. It is shown that F intake exerts the most significant effects upon liver microsomal properties, e.g. higher fluidity, cyt P450 content and enzymatic activities, an effect that prevails over the intake of the supplements tested.

The re-emergence of American visceral leishmaniasis in an old focus in Venezuela: present situation of human and canine infections

The report of a new autochthonous case of human American Visceral Leishmaniasis (AVL) in 1992 in the village of Guayabita, Aragua State, Venezuela (10 degrees 16'N, 67 degrees 28'W; 500 m asl), led us to undertake an epidemiological study in this locality. A demographic survey was conducted using a structured questionnaire in which data was collected regarding sex, age, occupation, length of residence in the area and migratory history. A leishmanin skin test (LST) was applied and samples of venous blood for counter immunoelectrophoresis (CIEP) and immunofluorescent antibodies (IFAT) tests were drawn. The prevalence of positive LST was 11.4%. The positivity was highest among males and increased with age. Young males seemed to be more exposed to infection than females. Since occupation per se did not seem to account for this association, it may be explained as a gender-associated behavior, leading to different degrees of exposure to sand flies. The canine population was also screened for leishmanial infection. One dog was shown to be parasitologically infected with Leishmania sp. Four out of 71 dogs (5.6%) were positive for FG, CIEP, IFAT and Western Blot and 11 (15.5%) were positive for CIEP. These results suggest that after almost 30 years of epidemiological silence, American visceral leishmaniasis has re-emerged in this focus.

Two distinct oncornaviruses harbor an intracytoplasmic tyrosine-based basolateral targeting signal in their viral envelope glycoprotein

It has been clearly established that the budding of the human immunodeficiency virus (HIV-1), a lentivirus, occurs specifically through the basolateral membrane in polarized epithelial cells. More recently, the signal was assigned to a tyrosine-based motif located in the intracytoplasmic domain of the envelope glycoprotein, as previously observed on various other viral and cellular basolateral proteins. In the present study, expression of human T-cell leukemia virus type 1 (HTLV-1) or Moloney murine leukemia virus envelope glycoproteins was used for trans-complementation of an envelope-negative HIV-1. This demonstrated the potential of oncornaviral retrovirus envelope glycoproteins to confer polarized basolateral budding in epithelial Madin-Darby canine kidney cells (MDCK cells). Site-directed mutagenesis confirmed the importance of a common motif encompassing at least one crucial membrane-proximal intracytoplasmic tyrosine residue. The conservation of a similar basolateral maturation signal in different retroviruses further supports its importance in the biology of this group of viruses.

The cellular basis of aqueous outflow regulation

This review begins with an introduction to the concept of the cellular regulation of aqueous outflow, current methods used for its study, and the cell types that are known to participate in this process. Current research in the field is divided into work on cell properties, cell products and extracellular matrix, cytoskeletal and structural changes, and drug interactions.

Improvement of functional magnetic resonance images by pretreatment of data

Functional magnetic resonance images of the brains of subjects performing the finger-tapping paradigm were made using a conventional technique. Two threshold values for the pixels were obtained by analysing pixel by pixel the distributions of the means and variances of each subject's images for 20 consecutive scans, both while performing the task and while at rest. Considerable signal improvement in the final images was achieved by removing from our data all pixels beyond these threshold values (mean < or = 16 and variance > or = 7).

Clinical experience with the long-term use of 1% apraclonidine. Incidence of allergic reactions

OBJECTIVE

To identify the incidence and characteristics of allergic reactions associated with the long-term use of 1% apraclonidine hydrochloride.

METHODS

We undertook a retrospective analysis of 64 patients receiving long-term 1% apraclonidine therapy at the University of California-San Francisco Glaucoma Service. Patients were excluded if the duration of treatment was less than 2 weeks. Demographic data, initial intraocular pressure response, and incidence and characteristics of allergic reactions were obtained through chart review. Student's t test and chi 2 analysis were used to analyze the demographic data, and Kaplan-Meier survival analysis was used to estimate the long-term incidence of local reactions.

RESULTS

Sixty-four patients met the criteria for the study. Of these, 31 (48%) developed an allergic reaction (responders) that led to discontinuation of treatment with the medication, with a mean latency of 4.7 months. Mean follow-up was 13.3 months. Patients free of local reactions (nonresponders) for at least 10 months were able to successfully continue apraclonidine use. Responders tended to be older and female.

CONCLUSIONS

Our data are specific for the 1% preparation; however, physicians prescribing apraclonidine on a long-term basis should be aware of possible allergic reactions. A substantial percentage of patients developed this side effect, but most tolerated the medication for up to 4 months, and those without a local reaction after 10 months appeared to be able to continue apraclonidine use indefinitely. This allergic reaction is likely related to the adrenergic agent itself, and not to preservatives.

Determination of Cd, Cr, Cu, Pb and Zn in human semen by graphite furnace atomic absorption spectrometry after microwave sample dissolution

Human semen samples were analyzed by graphite furnace atomic absorption spectrometry, using L'vov platforms and the method of standard additions, to determine their Cd, Cr, Cu, Pb and Zn content. The samples were analyzed directly and after conventional and microwave wet acid dissolution. Matrix modification, using magnesium and palladium nitrates and ammonium biphosphate solutions, was evaluated for the analysis of the microwave-digested samples. The best results were obtained for Cr, Cu and Zn using Pd(NO3)2, and a mixture of Mg(NO3)2 and Pd(NO3)2 solutions. The direct analysis of water-diluted semen produced inaccurate results with unacceptably high standard deviations. The results obtained for the microwave-dissolved samples showed relative standard deviation values within the range 0.63-8.4%. The analysis of spiked semen solutions showed recoveries of the added analytes ranging from 96 to 104%. The accuracy of the measurements was checked against the NIST 1,577a, bovine liver, standard reference material. Sample dissolution time was drastically reduced from 3-4 hours, using the conventional method, to approximately 8 minutes using the microwave-assisted wet acid digestion procedure.

[The development of the anti-phospholipase A2 antibody response in horses inoculated with venom for the production of polyvalent antisnake serum in Costa Rica]

The development of antibody response against phospholipase A2 activity of Bothrops asper venom was studied in a group of adult and healthy horses used in the production of the polyvalent antivenom at the Instituto Clodomiro Picado. Simultaneously, the general condition of the animals during the immunization schedule was also studied. There was a great individual variability in the immune response, although most of the horses studied reached the highest neutralizing titer after injection of doses of venom of 30 mg and 50 mg. On the other hand, in horses that had been previously immunized and were infected for a second immunization, the highest antibody titer was observed 16-22 days after inoculation. There were only mild alterations in the general condition of the horses as a consequence of venom inoculation. However, local abscesses, fistulae and fibrosis were observed at the site of venom injection. On the basis of the conspicuous individual variability observed, it is proposed that the immune response in horses used in the production of antivenom must be evaluated on individual basis, instead of working with pools of serum samples.

Effects of betaxolol/timolol on epinephrine stimulated cyclic-AMP levels in human trabecular meshwork cells

The effects of timolol and betaxolol were compared for blocking beta agonist stimulation of cyclic-AMP in cultured human trabecular meshwork cells. Epinephrine (10(-5) M) produced a large and rapid increase in HTM cyclic-AMP; timolol (10(-6) M), at concentrations readily achieved in the aqueous humor after 0.5% eyedrops, completely blocked this effect. Recovery from timolol treatment appeared to be relatively slow, with only a 30-40% recovery observed by 9 hours. In comparison, betaxolol (10(-6) M) produced a smaller blockade of the epinephrine effects; a rapid recovery from the betaxolol effects was observed, with a greater than half-maximal response to epinephrine observed 15 minutes after removal of this beta blocker. These findings may help to explain the clinical observations of an outflow facility effect of epinephrine when used in combination protocols with betaxolol, but not with timolol.

Characterization of beta-adrenergic receptors in cultured human trabecular cells and in human trabecular meshwork

The characterization of beta-adrenergic receptors on cultured human trabecular cells and trabecular meshwork from human autopsy eyes was carried out by radioligand binding utilizing (125I)-iodopindolol. In cultured cells, the observed binding of (125I)-iodopindolol was of high affinity (Kd = 43 pM) and saturable. Scatchard plots were linear and revealed a Bmax of 33 +/- 7 fmol/mg of protein. Competition studies with a series of agonists and antagonists revealed that human trabecular cells contain a single class of beta-adrenergic receptors of the beta 2 subtype. Similarly, the IC50 of ICI 89,406 (176 nM) in human trabecular meshwork from autopsy eyes supports the presence of beta 2-adrenergic receptors in this tissue.

Use of immunotoxin to inhibit proliferating human corneal endothelium

Transferrin plays a central role in cellular proliferation and proliferating cells have been shown to express transferrin receptors with increased density. We examined the effect of an immunotoxin consisting of anti-transferrin receptor monoclonal antibody (454A12) conjugated to recombinant ricin A chain (rRTA) on the proliferation of human corneal endothelium (HCE) in vitro. In proliferating cultures an immunotoxin (454A12-rRTA) concentration of 50 ng/mL reduced cell counts at day 7 by at least 89%, with no effect observed at 0.01 ng/ml. In contrast, cell counts were only minimally reduced in confluent cultures, even after 7 days' exposure to high concentrations of immunotoxin. These data suggest that 454A12-rRTA may be used to prevent growth of human corneal endothelium in pathological conditions such as the iridocorneal endothelial (ICE) syndrome.

The cytoskeleton of the cultured human trabecular cell. Characterization and drug responses

To determine the organization of the three major cytoskeletal elements of cultured human trabecular meshwork cells (actin filaments, microtubules and intermediate filaments), we employed fluorescence microscopy and stereo-transmission electron microscopy of extracted, S-1 labeled and critical-point dried cells. Morphologic changes resulting from treatment with cytochalasin B, colchicine, taxol and nocodozole were also characterized. Compared with the cynomolgus monkey trabecular cell, morphologic differences in overall cell shape and orientation of both actin filaments and microtubules were noted. However, the responses to cytoskeletal active drugs were quite similar. Taxol, nocodozole and colchicine had a marked effect on microtubule organization, while nocodozole and colchicine had a marked effect on vimentin filament organization. None of these drugs produced marked changes in human trabecular cell shape. In contrast, treatment with the anti-actin drug cytochalasin B resulted in both a marked change in cell shape associated with organizational changes in all three cytoskeletal elements. These studies suggest a central role of actin filaments in determining overall cell shape and cytoskeletal organization in the cultured human trabecular cell.

Subconjunctival injections. Preservative-related changes in the corneal endothelium

The morphologic effects on rabbit corneal endothelium of several common ophthalmic vehicle constituents were examined following subconjunctival administration. Profound dose-dependent changes consisting of intercellular vacuolization and thickening of the endothelial layer were noted within 1 day following administration of solutions that contained sodium bisulfite or methylparaben and propylparaben. These changes persisted for at least 5 days except in those eyes treated with the lowest concentration of sodium bisulfite. In contrast, administration of sodium citrate and creatinine or unpreserved normal saline resulted in only minimal effects. These changes are of concern because these agents are present in many preparations used to treat a wide variety of eye diseases.

Prenatal and postnatal growth of the human Descemet's membrane

The origin, growth in thickness, and differentiation of Descemet's membrane was studied by light, electron microscopic, morphometric, and statistical methods in 67 specimens from 12 weeks of gestation to 98 years. Descemet's membrane is formed by three major processes: growth in thickness during the prenatal period, prenatal differentiation into a striated basement membrane, and growth in thickness during the postnatal period. The initial step is the synthesis of an ordinary basement membrane, which is very thin and quite different in appearance from the adult Descemet's membrane. Growth of the prenatal Descemet's membrane then proceeds by deposition of a series of similar "membrane units," which are stacked to form a lamellar structure consisting of at least 30 layers by the end of gestation. Second, during prenatal life, differentiation of the membrane leads to the formation of a striated structure through the gradual addition of short and thin cross-linking bridges separated by 110-nm intervals that are disposed in a plane perpendicular to the lamellae. The third process occurs in postnatal life when the membrane continues to grow in thickness by deposition of a nonstriated, nonlamellar material posterior to the striated prenatal layer. Regression analysis suggests that prenatal growth proceeds at a rapid but variable rate best described by a "sigmoid-like" function of age. Postnatal growth, in contrast, proceeds in a predominantly exponential manner but at a slower pace than in the prenatal period. The low variability and large size of our set of measurements make these data especially useful for comparisons with pathologic specimens.

Trabecular meshwork cellularity in primary open-angle glaucoma and nonglaucomatous normals

The trabecular meshwork cellularity (cells/unit tissue area) was compared in patients with primary open-angle glaucoma (POAG) with that of nonglaucomatous (NG) individuals. The NG specimens (n = 69) include specimens from the prenatal period (n = 14) as well as the postnatal period to age 98 years (n = 55). The glaucoma specimens (n = 49) covered a wide-range of ages (23-80 years) and were obtained at trabeculectomy (n = 31) or at autopsy (n = 18). Our results show that the trabecular cellularity in NG specimens decreases most rapidly and in a nonlinear manner in the late fetal period and for the first few years of postnatal life. This rapid decline in cellularity then slows down to proceed in a nearly linear manner for the remainder of the 98 years of life studied. The meshworks from patients with POAG have a lower cellularity than normals over the wide range of ages examined, but both types of specimens undergo similar declines in cellularity with age. Thus, the age-cellularity curves for both the NG and POAG specimens are parallel to each other. The loss of cells occurs in a gradient-like manner with the inner tissues being most affected and the outermost tissues least affected. A variety of statistical tests show that these changes in cellularity are highly significant and specific. These findings are compared to the loss of endothelial cells in the cornea and they are discussed in relation to the important clinical characteristics of POAG.

Prenatal and postnatal cellularity of the human corneal endothelium. A quantitative histologic study

The authors studied the cellularity of the normal corneal endothelium by histologic methods in 56 specimens from 16 weeks of gestation to 98 years of age. Ten step-serial sections were taken from each specimen through the central 6 mm of the cornea, in an area measuring 1.8 mm. The number of nuclei were counted on each section and a ratio of the number of nuclei per 100 micron of endothelial length was determined. This ratio provides a measure of cell density that they call cellularity. There is a decrease in cellularity that proceeds in a nonlinear manner and at a very rapid rate during the prenatal period and for the first few years of life. Cell death or necrosis, which might have contributed to this apparent loss of cells, was not observed. Instead, this rapid change in cellularity is correlated with a concomitant change in corneal size. The authors' calculations show that cell division may play a minor role in the formation of the endothelium after the second trimester of fetal life as most of the cells present by birth already exist by this time. After the first few years of life, the rate of change in endothelial cellularity decreases to proceed in a linear manner for the rest of the near 100 years of life examined. This latter age-related decline in cellularity is probably due to the loss of 0.56% cells per year from the endothelial layer, since the cornea does not appear to change in size during this time. Statistical analysis of the authors' data shows that these results are highly significant.

Age-related changes in the basement membrane of the human corneal epithelium

An ultrastructural evaluation and morphometric analysis of the basement membrane of the normal human corneal epithelium in 45 specimens from subjects ranging in age from 17 weeks of gestation to 93 years was conducted. It was found that thickening of the corneal epithelial basement membrane takes place by two main processes: continued membrane deposition (forming unilaminar membranes) and membrane reduplication (forming multilaminar membranes). During the fetal period and for the first two decades of postnatal life, membrane thickening occurs exclusively by continued membrane deposition so that these unilaminar membranes increase in thickness by 3 nm each year. Membrane reduplication in focal areas after the age of 20 and with increasing frequency and greater involvement of the membrane thereafter was observed. Since anchoring fibrils and hemidesmosomes are important in the adhesion of the epithelium to Bowman's layer, we paid particular attention to these structures. We could find no relation between hemidesmosome content and the formation of reduplicated or multilaminar membranes. However, the anchoring fibrils become disrupted with increasing age, and the membrane thickness exceeds fibril length in some specimens. It is proposed that this phenomenon effectively blocks linkage between the anchoring fibrils and Bowman's layer. The evidence for cell injury and death as a promoter of membrane reduplication was compared to the evidence for a primary deterioration of the basement membrane.

Immunotherapy with a mixture of Mycobacterium leprae and BCG in different forms of leprosy and in Mitsuda-negative contacts

A total of 529 weak or non-reactors to M. leprae, including Mitsuda-negative contacts and patients with leprosy, were vaccinated once or repeatedly, as necessary, with a mixture of 6 x 10(8) purified, heat-killed M. leprae and 0.01 mg to 0.2 mg of viable BCG. Clinical, histopathological and immunological criteria were used to evaluate the response of these individuals. Clinical changes, including sharper definition of borders and progressive flattening and regression of lesions, were observed in 57% of the active LL cases and 76% of the active BL cases. Histopathological study revealed infiltration of the lesions by mononuclear cells, appearance of epithelioid differentiation, and fragmentation of the microorganisms. Delayed-type skin tests with soluble antigen from purified M. leprae became positive in significant numbers of each group studied. These results demonstrate the efficacy of combined immunotherapy in low-resistance forms of leprosy and potential utility in the immunoprophylaxis of the disease.

Age-related changes in trabecular meshwork cellularity

To investigate whether alterations in the cellular component of the trabecular meshwork occur with age, we evaluated trabecular meshwork cellularity and absolute cell number, using specimens obtained from patients ranging in age from newborn to 81 years. We obtained reproducible, quantitative measurements of these parameters, using montages of 1 micrometer meridional sections. A progressive decrease in cellularity (58%) and absolute cell number (47%) in the trabecular meshwork occurred over the 81-year period studied. Regression analysis suggested that the decrease in cellularity and cell number is linear function of age, resulting from a loss of approximately 0.58% of all cells per year. This change in cellularity parallels that seen in the corneal endothelium. implying that trabecular cells, like corneal endothelial cells, may have a limited reparative capacity.